1. Field of the Invention
The present invention relates to a control apparatus for controlling a marine vessel propulsion system equipped with a steering mechanism and a propeller system, and a marine vessel running supporting system and a marine vessel equipped with such a control apparatus.
2. Description of Related Art
There is an electromotive outboard motor that is one type of marine vessel propulsion system to provide a propulsive force to a marine vessel. The electromotive outboard motor is mainly used in places where the use of an engine type outboard motor is prohibited in view of environmental protection, such as in a lake.
The electromotive outboard motor includes a propeller system having an electric motor and a propeller coupled with the drive shaft of the electric motor, wherein, by controlling the rotational speed of the electric motor, it is possible to control a propulsive force generated by the propeller system, and by controlling the direction (steering angle) of the propulsive force generated by the propeller system, it is possible to control the advancing direction of a marine vessel.
An electromotive outboard motor disclosed in U.S. Pat. No. 5,931,110 is mainly used for short-distance movements and adjustment of the stem direction in a small-sized fishing boat, for example, a bass fishing boat. Further, in U.S. Pat. No. 5,931,110, a so-called auto pilot function is disclosed. The auto pilot automatically controls the steering angle and the rotational speed of an electric motor such that a vessel keeps a position in which the stem is oriented in a fixed direction at all times.
In the following description, not only in an electromotive outboard motor but also a general outboard motor, a motor (including an electric motor and an engine) and a propeller (propulsive force generation member) are collectively called a “propeller system”. Also, a mechanism for controlling the direction (steering angle) of a propulsive force generated by the propeller system is called a “steering mechanism”. In the steering mechanism, an electric motor and other electromotive power source which are driven by electric energy, and hydraulic equipment may generate power to change the steering angle. In addition, there is a case where a portion of a drive force generated by a motor may be used to change the steering angle. The propeller system and the steering mechanism are collectively called a “marine vessel propulsion system”. It is common that the outboard motor is additionally provided with a steering mechanism in addition to the propeller system. Such an outboard motor is included in the definition of the above-mentioned marine vessel propulsion system.
In a marine vessel maneuvering mechanism disclosed in Japanese Unexamined Patent Publication No. 02-227395, the steering angles of respective propeller systems are controlled by expanding and contracting a cylinder rod which intervenes between two propeller systems, via an electric pump driven by a control motor.
Since a motor whose output is smaller than the propeller system is usually used as a motor of the steering mechanism, the steering mechanism generally includes a reduction mechanism that reduces a drive force generated by the motor and transmits the reduced drive force. Therefore, the time required to reach a target steering angle becomes comparatively long. In particular, as the propeller system becomes large in size, a reduction mechanism whose reduction ratio is correspondingly large is used. Therefore, the time to reach a target steering angle is increased.
On the other hand, since a propeller system rotates a propeller directly by an electric motor or an engine, or rotates the propeller after being reduced at a small reduction ratio, a target propulsive force can quickly be reached. Accordingly, where respective controls of a propeller system and a steering mechanism are simultaneously started based on respective target values, the propulsive force will reach the target value earlier than the steering angle reaches the target value. In this case, since a propulsive force is generated in the hull in a direction not intended by an operator for the period from immediately after the time when the steering angle begins changing to the time when the target value is reached, there is a possibility that a desired ship behavior cannot be achieved.